1. Field of the Invention
Embodiments of the present invention generally relate to tools and methods for hanging and/or expanding liner strings.
2. Description of the Related Art
In wellbore construction and completion operations, a wellbore is initially formed to access hydrocarbon-bearing formations (i.e., crude oil and/or natural gas) by the use of drilling. Drilling is accomplished by utilizing a drill bit that is mounted on the end of a drill support member, commonly known as a drill string. To drill within the wellbore to a predetermined depth, the drill string is often rotated by a top drive or rotary table on a surface platform or rig, or by a downhole motor mounted towards the lower end of the drill string. After drilling to a predetermined depth, the drill string and drill bit are removed and a section of casing is lowered into the wellbore. An annulus is thus formed between the string of casing and the formation. The casing string is temporarily hung from the surface of the well. A cementing operation is then conducted in order to fill the annular area with cement. The casing string is cemented into the wellbore by circulating cement into the annulus defined between the outer wall of the casing and the borehole. The combination of cement and casing strengthens the wellbore and facilitates the isolation of certain areas of the formation behind the casing for the production of hydrocarbons.
It is common to employ more than one string of casing or liner in a wellbore. In this respect, the wellbore is drilled to a first designated depth with a drill bit on a drill string. The drill string is removed. A first string of casing is then run into the wellbore and set in the drilled out portion of the wellbore, and cement is circulated into the annulus behind the casing string. Next, the wellbore is drilled to a second designated depth, and a second string of casing or liner, is run into the drilled out portion of the wellbore. If the second string is a liner, the liner string is set at a depth such that the upper portion of the second liner string overlaps the lower portion of the first string of casing. The second liner string is then fixed, or “hung” off of the existing casing using a liner hanger to fix the new string of liner in the wellbore. The second liner string is then cemented. A tie-back casing string may then be landed in a polished bore receptacle (PBR) of the second liner string so that the bore diameter is constant through the liner to the surface. This process is typically repeated with additional liner strings until the well has been drilled to total depth. As more casing or liner strings are set in the wellbore, the casing or liner strings become progressively smaller in diameter in order to fit within the previous casing string. In this manner, wells are typically formed with two or more strings of casing and/or liner of an ever-decreasing diameter.
The process of hanging a liner off of a string of surface casing or other upper casing string involves the use of a liner hanger. The liner hanger is typically run into the wellbore above the liner string itself. The liner hanger is actuated once the liner is positioned at the appropriate depth within the wellbore. The liner hanger is typically set through actuation of slips which ride outwardly on cones in order to frictionally engage the surrounding string of casing. The liner hanger operates to suspend the liner from the casing string. However, it does not provide a fluid seal between the liner and the casing. Accordingly, a packer may be set to provide a fluid seal between the liner and the casing.
During the wellbore completion process, the packer is typically run into the wellbore above the liner hanger. A threaded connection typically connects the bottom of the packer to the top of the liner hanger. Known packers employ a mechanical or hydraulic force in order to expand a packing element outwardly from the body of the packer into the annular region defined between the packer and the surrounding casing string. In addition, a cone is driven behind a tapered slip to force the slip into the surrounding casing wall and to prevent packer movement. Numerous arrangements have been derived in order to accomplish these results.
The cementing process typically involves the use of liner wipers and drill-pipe plugs. A liner wiper is typically located inside the top of a liner, and is lowered into the wellbore with the liner at the bottom of a working string. The liner wiper plug typically defines an elongated elastomeric body used to separate fluids pumped into a wellbore. The wiper has radial wipers to contact and wipe the inside of the liner as the wiper travels down the liner. The liner wiper has a cylindrical bore through it to allow passage of fluids.
After a sufficient volume of cement has been placed into the wellbore, the plug is deployed. Using a displacement fluid, such as drilling mud, the plug is pumped into the working string. As the plug travels downhole, it seats against the liner wiper, closing off the internal bore through the liner wiper. Hydraulic pressure above the plug forces the plug and the wiper to dislodge from the bottom of the working string and to be pumped down the liner together. This forces the circulating fluid or cement that is ahead of the wiper plug and dart to travel down the liner and out into the liner annulus.